Theta rhythms in the rat medial entorhinal cortex in vitro: evidence for involvement of muscarinic receptors.

Slice preparation obtained from the rat were used to study cholinergically induced field potentials in the medial entorhinal cortex. Perfusion of slices containing medial entorhinal cortex with acetylcholine, muscarine and eserine induced theta-like activity in a frequency range of 3-10 Hz and an amplitude of 200-300 microV. Nicotine, in contrast, did not produce any rhythmical slow waveforms. The cholinergically induced theta-like oscillations were abolished by perfusion of the muscarinic antagonists atropine sulphate and scopolamine but were unaffected by the nicotine blockers hexamethonium and mecamylamine.